If you create a CBZip2OutputStream and immediately close it you get an 
ArithmeticException.

If you create a CBZip2InputStream with no input you get a 
NullPointerException.  GZIPInputStream throws a EOFException which makes more 
sense.

Example:

import org.apache.tools.bzip2.*;
import java.io.*;

public class AntBug {
    public static void main(String[] args) {
	try {
	    CBZip2InputStream cb =
		new CBZip2InputStream(new ByteArrayInputStream(new byte[0]));
	    cb.close();
	} catch (Exception e) {
	    e.printStackTrace();
	}
	try {
	    CBZip2OutputStream cb =
		new CBZip2OutputStream(new ByteArrayOutputStream());
	    cb.close();
	} catch (Exception e) {
	    e.printStackTrace();
	}
    }
}

Produces:

java.lang.NullPointerException
        at org.apache.tools.bzip2.CBZip2InputStream.bsR
(CBZip2InputStream.java:285)
        at org.apache.tools.bzip2.CBZip2InputStream.bsGetUChar
(CBZip2InputStream.java:303)
        at org.apache.tools.bzip2.CBZip2InputStream.initBlock
(CBZip2InputStream.java:192)
        at org.apache.tools.bzip2.CBZip2InputStream.<init>
(CBZip2InputStream.java:140)
        at AntBug.main(AntBug.java:7)
java.lang.ArithmeticException: / by zero
        at org.apache.tools.bzip2.CBZip2OutputStream.mainSort
(CBZip2OutputStream.java:1135)
        at org.apache.tools.bzip2.CBZip2OutputStream.doReversibleTransformation
(CBZip2OutputStream.java:1347)
        at org.apache.tools.bzip2.CBZip2OutputStream.endBlock
(CBZip2OutputStream.java:438)
        at org.apache.tools.bzip2.CBZip2OutputStream.close
(CBZip2OutputStream.java:389)
        at AntBug.main(AntBug.java:16)